04 GMC coolant and oil problem

So I noticed my temp was high and checked my coolant which required a gallon of fluid to be added. Around the same time there came a light clatter from the engine when I would start it. The clatter would persist for a minute or so then fade away. I changed the oil and the clatter quit.
The engine light also came on with a code indicating one bank was running too lean. Cleared the code and it hasn't come back on.

1,600 miles later (just at one month) engine hot again requiring another gallon of coolant and valve clatter is back.

I'm at the dealer now getting this diagnosed. They have ruled out the intake gasket with a pressure test and are saying it's either a cracked head or a head gasket. They are estimating repairs at $1800 for a head gasket and have not mentioned a price for a new head. They are currently popping the valve covers to look for cracks.

Does this sound like bull? Are the heads relatively easy to do by one's self (I've got more auto experience than most peoeple, but I'm not a mechanic - I've replaced lower intake gasket, control arm bushings, transmissions, etc)? OR does someone here know of some secret problem with this engine that would be a likely culprit?

04 gmc 1/2 ton with the little 4.8 "v" engine

thanks

Oh, the truck has 86,000 miles and I'm relatively hard on it, but I take good care of it. Gets regular oil changes and royal purple synthetic oil.

So it turns out the right head is cracked. apparently this is a well known problem and I get to spend $3,000 on the project of they said I could have a brand new engine for $5,000 haha. It really made me want to punch the guy.

Any ideas where to buy heads for a reasonable price? Apparently the key is to avoid Castech heads, as they are the ones experiencing this failure. The dealer wants about $450 per head for them, but I have a sneaking suspicion that a motivated individual could do better than that.

Anyone know of a good place to get quality heads for a more reasonable price?